Wafer drying apparatus

ABSTRACT

An apparatus for drying a semiconductor substrate includes a chamber having a processing bath and a cover, a liquid flow system for supplying a liquid flow into the processing bath so as to clean the substrate and for draining a liquid from the processing bath, a gas distributor for spraying a gas for drying the substrate, and decompression means for exhausting air in the chamber.

RELATED APPLICATION

[0001] This application relies for priority upon Korean Patent Application No. 2001-87114, filed on Dec. 28, 2001, the contents of which are herein incorporated by reference in their entirety.

FIELD OF THE INVENTION

[0002] The present invention relates to an apparatus for fabricating a semiconductor device used in a wafer cleaning process and, more particularly, to an apparatus for drying a wafer subjected to a cleaning process.

BACKGROUND OF THE INVENTION

[0003] As semiconductor devices are continuously scaled down, the wafer cleaning techniques have been diversified and increasingly significant. Particularly in a process for fabricating semiconductor devices having a fine structure, particles attached to a cleaned wafer, static electricity, watermarks, and linear particles have a great effect on subsequent processes. Therefore, what is needed is a wafer drying process.

[0004] There were suggested a spin dryer and an IPA vapor dryer. In drying a wafer, the spin dryer uses a centrifugal force while the IPA vapor dryer uses a low vapor pressure of isopropyle alcohol (IPA). However, the dryers cannot completely remove watermarks that occur on a wafer surface or between patterns. In order to avoid this problem, a Marangoni dryer has been widely used. The Marangoni dryer uses a difference between surface tenses of the IPA and water.

[0005] A drying process using the Marangoni effect will now be described in brief hereinbelow.

[0006] After wafers are rinsed out by de-ionized water (hereinafter referred to as “DIW”), the IPA vapor is fed to an upper interior space of a rinsing bath and the DIW is slowly withdrawn. Thus, the water is eliminated from a wafer surface. When the DIW is completely drained, the nitrogen of high temperature is fed thereinto to evaporate the DIW remaining on the wafer surface. Unfortunately, the evaporated DIW and residues including particles are not fully issued out. They cause the irregular liquid flow (turbulence) in the rinsing bath together with the nitrogen, so that the wafer surface is not uniformly dried and the water remains at a portion contacting with a wafer guide. In addition, since the Marangoni dryer cannot fundamentally prevent oxygen from reacting on the wafer, it cannot suppress formation of an oxide layer.

SUMMARY OF THE INVENTION

[0007] A feature of the present invention to provide a wafer drying apparatus that fundamentally prevents oxygen from reacting on a wafer surface during a wafer drying process to suppress formation of an oxide layer.

[0008] Another feature of the present invention is to provide a wafer drying apparatus that improves a wafer drying efficiency.

[0009] Still another feature of the present invention is to provide a wafer drying apparatus that suppresses the turbulence in a processing bath.

[0010] To achieve these features, the present invention provide a wafer drying apparatus in which a gas used to dry a wafer smoothly flows from an upper part to a lower part of a processing bath and is smoothly discharged to improve a wafer drying efficiency. This wafer drying apparatus includes an injection port for injecting a dry gas into the processing bath to eliminate water remaining on a wafer, decompression means for decompressing an inside of the processing bath, and an exhaust pipe through which the injected dry gas and residues including vapor dried by the dry gas are exhausted. The exhaust pipe communicates with a drain pipe for draining a process solution filling the processing bath. The drain pipe is comprised of a first drain pipe for draining the process solution and a second drain pipe for draining the process solution slower than the first pipe. The exhaust pipe is connected to the first exhaust pipe, and is mounted upon the cover.

[0011] The wafer drying apparatus further includes a sealing member for sealing between the processing bath and the cover. The sealing member may be an O-ring or a gasket.

[0012] According to another aspect of the invention, an apparatus for drying a semiconductor substrate includes a chamber having a processing bath with which a liquid is filled and a cover mounted upon the processing bath, a gas distributor for spraying a gas for drying the substrate from an upper part of the processing bath, a liquid flow system for supplying a liquid flow into the processing bath so as to clean the substrate and for draining a liquid from the processing bath, decompression means for exhausting air in the chamber, and means for exhausting the gas supplied into the chamber.

[0013] The gas distributor includes first and second nozzles mounted upon the cover. The decompression means includes an exhaust port formed at the cover, a first exhaust pipe connected to the exhaust port, and a valve for shutting on/off the first exhaust pipe. The liquid flow system controls the liquid flow and drain together with the gas distributor to achieve the Marangoni effect. The apparatus further includes means for forcibly exhausting the gas supplied into the chamber. The forcibly exhausting means includes a second exhaust pipe connected to the drain pipe and an on/off valve for shutting on/off the second drain pipe.

BRIEF DESCRIPTION OF THE DRAWINGS

[0014]FIG. 1 is a cross-sectional view for explaining a wafer drying apparatus in accordance with an embodiment of the present invention.

[0015] FIGS. 2 through FIG. 6 are cross-sectional views showing the wafer drying steps in accordance with the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT

[0016] The preferred embodiment of the present invention and its advantages are best understood by referring to attached drawings, like numerals being used for like and corresponding parts of the various drawings.

[0017] Referring now to FIG. 1, a wafer drying apparatus 100 made according to the invention includes a chamber 110, a gas distributor 130, a liquid flow system, and decompression means.

[0018] The chamber 110 has a processing bath 112 and a cover 114. The processing bath 112 includes a bottom 112 a, sidewalls 112 b, and an exhaust port 113. The processing bath 112 provides a space that is surrounded by the bottom 112 a and the sidewalls 112 b. The exhaust port 113 is extended from the bottom 112 a of the processing bath 112. In an upper part of the processing bath 112, there is an opening that is opened and closed by the cover 114. An O-ring 116 is installed to seal between the cover 114 and the processing bath 112.

[0019] Wafers W in the processing are supported by a wafer guide 120. The wafer guide 120 may be comprised of at least three bars 122 a and 122 b that are perpendicularly disposed to the wafers W. For example, the wafer guide 120 is comprised of one central bar 122 a and two side bars 122 b disposed at both sides of the central bar 122 a. The wafer guide 120 may be connected to a lift (not shown) for lifting up/down the wafers W.

[0020] The gas distributor 130 is installed at the cover 114 and includes an IPA nozzle 132 and N2 nozzles 134. Supply pipes 136 a and 136 b are connected to the IPA nozzle 132 and the N2 nozzles 134, respectively. Undoubtedly, the supply pipes 136 a and 136 b are connected to an IPA supply source (not shown) and an N2 supply source (not shown), respectively. The IPA and N2 used to dry a wafer are uniformly fed to the space of the processing bath 112 through the IPA nozzle 132 and the N2 nozzle 134.

[0021] The gas distributor 130 supplies IPA and an inert gas such as high-temperature or heated nitrogen into the processing bath 112 from an upper part of the processing bath 112.

[0022] The liquid flow system has supply means for continuously supplying a liquid into the processing bath 112 and drain means for continuously draining the liquid from the processing bath 112. The level and drain of the liquid are controlled by the supply means and the drain means. The supply means includes a distribution pipe 142 that is installed along the wafer guide 120 and has a number of injection holes 144. The distribution pipe 142 receives a liquid from an external liquid supply source through a liquid supply pipe. The drain means includes first and second drain pipes 152 a and 152 b and a control valve 154. The first and second drain pipes 152 a and 152 b are connected to the exhaust port 113 of the processing bath 112. The control valve is installed at the respective drain pipes 152 a and 152 b. For example, a diameter of the second drain pipe 152 b is preferably smaller than that of the first drain pipe 152 a so as to drain a solution slower than the first drain pipe 152 a. The level of the liquid used in a clearing process is controlled by the control valve 154. The clearing process is a process for cleaning or rinsing the wafers W. In a case where the cleaning process is for cleaning the wafers W, the liquid may be a chemical solution that is suitable for clearing contaminants such as particles remaining on the wafers W or a native oxide layer. In a case where the cleaning process is for rinsing the wafers W, the liquid may be a de-ionized water (DIW) that is suitable for clearing a chemical solution remaining on the wafers W.

[0023] The decompression means includes an exhaust port 162, a vacuum exhaust pipe 164 connected to the exhaust port 162, and an on/off valve for shutting on/off the vacuum exhaust pipe 164. Before supplying the IPA, the decompression means decompresses the chamber 110 so as to exhaust air (practically, oxygen) therein. After rinsing the wafer W, the air staying in a space “a” between the processing bath 112 and the cover 114 is exhausted through the exhaust port 162 to prevent the wafer W from reacting on the oxygen in the air. Therefore, it is possible to suppress formation of watermarks caused by the oxidation of a wafer surface.

[0024] The wafer drying apparatus 100 further includes means for forcibly exhausting the IPA and N2 supplied into the chamber 110. The forcibly exhausting means has a first exhaust pipe 172 connected to the first drain pipe 152 a and an on/off valve 174 for shutting on/off the exhaust pipe 174. The on/off value 174 is closed when the solution in the processing bath 112 is drained, and is opened after the solution is completely drained or when the N2 is supplied. More specifically, after the solution is completely drained, the N2 is injected from the N2 nozzle 134 installed at the cover 114. When vacuum exhaustion is conducted through the drain port 113, an up-to-down flow is created in the processing bath 112. The up-to-down flow allows vapor, residues containing particles, and N2 to be exhausted quickly and surely to the first exhaust pipe 172 through the drain port 113.

[0025] A wafer drying method according to the present invention will now be described more fully hereinbelow with reference to FIG. 2 through FIG. 6.

[0026] The wafers W are loaded in the processing bath 112. De-ionized water (DIW) is supplied into the processing bath 112 through the distribution pipe 142. The DIW is continuously supplied and drained through the supply means and the drain means in order to rinse the wafers W (see FIG. 2). After rinsing the wafers W, the chamber 110 is decompressed to exhaust air therein (see FIG. 3). That is, the decompression means is used to exhaust air staying in a space “a” between the cover 114 and the processing bath 112 containing the DIW. Nitrogen is supplied into the air-exhausted space “a” (see FIG. 4). In any case, the decompression and compression of the nitrogen are carried out at the same time. After filling the nitrogen with the space “a”, the IPA and nitrogen are supplied to an upper part of the DIW in the processing bath 112. Concurrently, the DIW is slowly drained through the second drain pipe 152 b (see FIG. 5). Thus, a drying process for eliminating DIW remaining on surfaces of the wafers W is carried out. More specifically, a part of the IPA penetrates into a surface of the DIW to lower a surface tension thereof. Particularly, when the wafers W rise or the DIW level drops during the drying process, a meniscus-shaped liquid surface is formed at a contact part of the surfaces of the wafers W and the DIW. Under these conditions, when the IPA is permeated into the DIW surface, the surface tension at the contact part is lower than that of any other part. The liquid remaining on the surfaces of the wafers W, i.e., the DIW flows toward a portion of high surface tension. As a result, the DIW is maximally eliminated from the surfaces of the wafers W according to the Marangoni effect. When the DIW level falls under the wafers W, the second drain pipe 152 b is closed and the first drain pipe 152 a is opened to swiftly drain the DIW remaining in the processing bath 112. The first drain pipe 152 a drains a solution by means of the gravity. When the DIW is completely drained from the processing bath 112, the final wafer drying process is followed as the next process. Referring to FIG. 5, the final wafer drying process uses heated nitrogen to eliminate particle-shaped DIW remaining on the wafer surface. More specifically, the heated nitrogen is supplied into the processing bath 112 through the N2 nozzle 134. The gases N2 and IPA for drying a wafer and residues including a fume are forcibly exhausted to the first exhaust pipe 172 through the drain port 113 of the processing bath 112. An up-to-down flow is then made in the processing bath 112, so that the residues, N2, and IPA are exhausted quickly and surely to the first drain pipe 172 through the drain pipe 113. Therefore, it is possible to prevent a turbulence from occurring in the processing bath 112. That is, a gas flow in the processing bath 112 can be stably maintained. If an unstable gas flow such as vortex occurs in the processing bath 112, it is hard to obtain a wafer particle drying effect that is achieved at a wafer surface by injecting N2 of high temperature. Accordingly, what is very significant is to stabilize and quickly exhaust a gas flow in the processing bath 112 during the wafer drying process. As a result, the N2 and residues are swiftly exhausted through the first exhaust pipe 172 during the wafer drying process. In addition, new N2 is supplied onto the wafer surface to minimize the wafer contamination caused by the residues and to maximize the water particle eliminating effect at the wafer surface.

[0027] Although the foregoing description of the preferred embodiments of the present invention has shown, described and pointed out the fundamental novel features of the invention, it will be understood that various omissions, substitutions and changes in the form of the detail of the apparatus as illustrated, as well as the uses thereof, may be made by those skilled in the art without departing from the spirit of the present invention. Consequently, the scope of the invention should not be limited to the foregoing discussion, but should be defined by the appended claims. 

What is claimed is:
 1. A wafer drying apparatus having a processing bath in which a wafer guide is placed and a cover for covering the processing bath, the wafer drying apparatus comprising: an injection port for injecting a dry gas into the processing bath to eliminate water remaining on a wafer; decompression means for decompressing an inside of the processing bath; and an exhaust pipe through which the injected dry gas and residues including vapor dried by the dry gas are exhausted.
 2. The apparatus as recited in claim 1, wherein the exhaust pipe communicates with a drain pipe for draining a process solution filling the processing bath.
 3. The apparatus as recited in claim 2, wherein the drain pipe is comprised of a first drain pipe for draining the process solution and a second drain pipe for draining the process solution slower than the first pipe; and wherein the exhaust pipe is connected to the first exhaust pipe.
 4. The apparatus as recited in claim 1, wherein the exhaust pipe is mounted upon the cover.
 5. The apparatus as recited in claim 1, further comprising a sealing member for sealing between the processing bath and cover.
 6. The apparatus as recited in claim 5, wherein the sealing member is an O-ring or a gasket.
 7. An apparatus for drying a semiconductor substrate, comprising: a chamber having a processing bath with which a liquid is filled and a cover mounted upon the processing bath; a gas distributor for spraying a gas for drying the substrate from an upper part of the processing bath; a liquid flow system for supplying a liquid flow into the processing bath so as to clean the substrate and for draining a liquid from the processing bath; and decompression means for exhausting air in the chamber.
 8. The apparatus as recited in claim 7, further comprising means for exhausting the gas supplied into the chamber.
 9. The apparatus as recited in claim 7, wherein the gas distributor includes first and second nozzles mounted upon the cover.
 10. The apparatus as recited in claim 7, wherein the decompression means includes: an exhaust port formed at the cover; a first exhaust pipe connected to the exhaust port; and a valve for shutting on/off the first exhaust pipe.
 11. The apparatus as recited in claim 7, wherein the liquid flow system controls the liquid flow and drain together with the gas distributor to achieve the Marangoni effect.
 12. The apparatus as recited in claim 7, wherein the liquid flow system has means for continuously draining the liquid from the processing bath or means for continuously supplying the liquid into the processing bath so as to control the level and drain of the liquid in the processing bath.
 13. The apparatus as recited in claim 12, wherein the means for continuously drain the liquid includes a drain pipe connected to the drain port of the processing bath and a control valve mounted upon the drain pipe, and the liquid level is controlled by the control valve.
 14. The apparatus as recited in claim 13, further comprising means for forcibly exhausting the gas supplied into the chamber, wherein the forcibly exhausting means includes: a second exhaust pipe connected to the drain pipe; and an on/off valve that is installed at the second exhaust pipe, and is closed when the liquid is drained and is opened after the liquid is completely drained.
 15. The apparatus as recited in claim 14, wherein the drain pipe is comprised of a first drain pipe and a second drain pipe whose diameter is smaller than a diameter of the first drain pipe so as to drain the solution slower than the first drain pipe.
 16. The apparatus as recited in claim 15, wherein the second exhaust pipe is connected to the first drain pipe.
 17. The apparatus as recited in claim 7, further comprising a guide for supporting the substrate in the processing bath, wherein the continuously liquid supplying means includes a distribution pipe that is installed along the guide and has a number of injection holes.
 18. The apparatus as recited in claim 7, further comprising a sealing member sealed between the processing bath and the cover, wherein the sealing member is an O-ring or a gasket.
 19. The apparatus as recited in claim 7, wherein the liquid is de-ionized water (DIW) and the gas is isopropyle alcohol (IPA) or nitrogen (N2). 